The present invention relates to metal chelates derived from a tetranitrogenous macrocycle condensed with a pyridyl nucleus, to their processes of preparation and to their application in medical imaging.
The use in imaging of chelates, with a paramagnetic or radioactive cation, of certain derivatives of this condensed macrocycle has been proposed on various occasions. Reference may be made to Patents EP-A-0,438,206, EP-A-0,570,575 and EP-A-0,579,802, which disclose compounds of formula 
in which X can be a carboxylate or phosphate group and R can be an alkyl or phenyl group or one of the R groups is a group forming a bond with a biological macromolecule.
Among these compounds, that for which Axe2x95x90Bxe2x95x90CH, R=H, X=CO2xe2x88x92 and M=Gd, known as PCTA, has been the subject of in-depth studies, described in Inorganic Chemistry, 36(14), 2992-3000 (1997) and Magn. Reson. Chem., 36, S200-208 (1998); the authors indicate in particular that PCTA is noteworthy in that it has a particularly high longitudinal relaxation r1, since it is approximately xe2x80x9c2 timesxe2x80x9d that of the gadolinium chelates used as contrast agents in magnetic resonance imaging in man.
It is known that r1 characterizes the effectiveness of paramagnetic products in generating a strong contrast of the images and it is especially advantageous and unexpected that the paramagnetic products of the invention exhibit relaxations r1 of 10 to 15 times greater than that of the commercial compounds, not only for a magnetic field of 0.5 tesla but also of 1 tesla, the field of most current imaging devices, and even at 1.5 tesla, the field of the devices with the best performances.
As these novel chelates, in addition to their favourable magnetic properties, are stable in vitro and in vivo, in particular with respect to possible breakdown of the complex, have a low osmolality and a good therapeutic index, and, according to the nature of the R group, can exhibit an excellent vascular persistence or an organ specificity, they will advantageously be used in man as contrast agents for magnetic resonance imaging or in nuclear medicine, when the metal ion is a radioelement.
The present invention relates to metal chelates of the compound of formula 
in which
R has the formula 
xe2x80x83and
Z is a bond or a group selected from the CH2, CH2xe2x80x94COxe2x80x94NH or (CH2)2xe2x80x94NHxe2x80x94CO groups,
Zxe2x80x2 is a bond or a group selected from the O, S, NQ, CH2, CO, COxe2x80x94NQ, NQxe2x80x94CO, NQxe2x80x94COxe2x80x94NQ or COxe2x80x94NQxe2x80x94CH2xe2x80x94COxe2x80x94NQ groups,
Zxe2x80x3 is a bond or a group selected from the COxe2x80x94NQ, NQxe2x80x94CO or COxe2x80x94NQxe2x80x94CH2xe2x80x94COxe2x80x94NQ groups,
p and q are integers, the sum of which has a value from 0 to 3,
R1, R2, R3, R4 and R5, independently of one another, are selected from the H, Br, Cl, I, COxe2x80x94NQ1Q2 and NQ1xe2x80x94COxe2x80x94Q2 groups, Q1 and Q2, which are identical or different, being H or (C1-C6)alkyl optionally interrupted by one or more oxygen atoms and at least one of the R1 to R5 groups being an amido group,
or R1, R3 and R5 are, independently of one another, H, Br, Cl or I, and
R2 and R4 have the formula 
xe2x80x83such that
Zxe2x80x2xe2x80x3 is a group selected from the COxe2x80x94NQ, CONQxe2x80x94CH2, COxe2x80x94NQxe2x80x94CH2xe2x80x94COxe2x80x94NQ, COxe2x80x94NQxe2x80x94(CH2)2xe2x80x94NQxe2x80x94CO and NQxe2x80x94COxe2x80x94NQ groups and Rxe2x80x21, Rxe2x80x23 and Rxe2x80x25, which are identical or different, are H, Br, Cl or I and Qxe2x80x21 and Qxe2x80x22, which are identical or different, are H or (C1-C6)alkyl optionally interrupted by one or more oxygen atoms,
Q is H or (C1-C4)alkyl,
the alkyl groups being optionally mono- or polyhydroxylated.
The metal ions can be paramagnetic ions, such as Gd3+, Fe3+, Tb3+, Mn2+, Dy3+ or Cr3+, or radioactive ions, such as 99mTc, 67Ga or 111In; the ions which form less stable chelates, which can give rise to transmetallation, such as Ca2+ or Zn2+, also form part of the invention; the paramagnetic chelates of Gd3+ and Mn2+ are particularly suited to magnetic resonance imaging. The paramagnetic chelates of Gd3+ are very particularly preferred.
It is preferable, for better hydrophilicity and biocompatibility of the compounds, for the R1 to R5 groups on the same phenyl ring together to comprise from 6 to 20 OH groups or even for any CONQ1Q2 group present, or, depending on the situation, CONQxe2x80x21Qxe2x80x22, to comprise from 6 to 10 OH groups; it is also preferable for R2 and R4 to be identical and to be COxe2x80x94NQ1Q2, which each comprise 6 to 10 OH groups, or the III group, in which each CONQxe2x80x21Qxe2x80x22 comprises from 6 to 10 OH groups; preference is also given to the compounds in which R1, R3 and R5 are selected from iodine or bromine atoms, as well as Rxe2x80x21, Rxe2x80x23 and Rxe2x80x25, when they are present.
The relaxation of the compounds and their in vivo pharmacokinetics depend in particular on their number of phenyl ring. For example, it is possible to distinguish the compounds in which p and q are 0, in particular when R2 and R4 are COxe2x80x94NQ1Q2, and those in which the sum of p and q has a value from 1 to 3 or better still 1 or 2 and R2 and R4 are or have not the formula III.
When, in the compounds of formula I, R2 and R4 are CONQ1Q2, Q1 and Q2 are preferably C2 to C6 alkyl groups optionally interrupted by an oxygen atom.
Furthermore, preference is given, among the compounds of formula I, to those in which Q is H and, among these, to those in which Z is CH2 or CH2CONH, Zxe2x80x2 is a group selected from CONH, CONHCH2CONH or NHCONH and Zxe2x80x3 from CONH and CONHCH2CONH, and it is also preferable, when it is present, for Zxe2x80x2xe2x80x3 to be CONH or CONHCH2CONH.
Finally, another group of specific compounds is composed of that in which, p and q being equal to 1, Z is CH2 or CH2CONH, Zxe2x80x2 and Zxe2x80x3 are selected from CONH and CONHCH2CONH, and R2 and R4 are CONQ1Q2, with R1, R3 and R5 preferably selected from Br and I.
Other preferred compounds are those defined in points (i) to (ix) hereinbelow:
(i) chelate of the compound of formula I in which p and q are 0 and R2 and R4, which are identical, are xe2x80x94COxe2x80x94NQ1Q2, each xe2x80x94COxe2x80x94NQ1Q2 group comprising from 6 to 10 xe2x80x94OH groups;
(ii) chelate of the compound of formula I in which p and q are 0, R1, R3 and R5 are identical and are selected from Br and I, and R2 and R4, which are identical, are xe2x80x94COxe2x80x94NQ1Q2, each xe2x80x94COxe2x80x94NQ1Q2 group comprising from 6 to 10 xe2x80x94OH groups;
(iii) chelate of the compound of formula I in which the sum p+q is not 0, any xe2x80x94COxe2x80x94NQ1Q2 group present comprises from 6 to 10 xe2x80x94OH groups, and R2 and R4 have not the formula III. Among these compounds, those for which p+q is 1 or 2 are more preferred.
(iv) Chelate of the compound of formula I in which the sum p+q is not 0, R1, R3 and R5 are identical and are selected from Br and I, and R2 and R4, which are identical, are xe2x80x94COxe2x80x94NQ1Q2, R2 and R4 each comprising from 6 to 10 xe2x80x94OH groups. Among these compounds, those for which p+q is 1 or 2 are more preferred.
(v) Chelate of the compound of formula I in which Z is CH2 or CH2xe2x80x94COxe2x80x94NH, Zxe2x80x2 is a group selected from COxe2x80x94NH, COxe2x80x94NHxe2x80x94CH2xe2x80x94COxe2x80x94NH and NHxe2x80x94COxe2x80x94NH, Zxe2x80x3 is a group selected from COxe2x80x94NH and COxe2x80x94NHxe2x80x94CH2xe2x80x94COxe2x80x94NH, R2 and R4, which are identical, are xe2x80x94COxe2x80x94NQ1Q2, R2 and R4 each comprising from 6 to 10 xe2x80x94OH groups, and R1, R3 and R5 are identical and are selected from Br and I. Among these compounds, those for which p+q is 1 or 2 are more preferred.
(vi) Chelate of the compound of formula I in which Z is CH2 or CH2xe2x80x94COxe2x80x94NH, Zxe2x80x2 is a group selected from COxe2x80x94NH, COxe2x80x94NHxe2x80x94CH2xe2x80x94COxe2x80x94NH or NHxe2x80x94COxe2x80x94NH, Zxe2x80x3 is selected from COxe2x80x94NH and COxe2x80x94NHxe2x80x94CH2xe2x80x94COxe2x80x94NH, Zxe2x80x2xe2x80x3, when it is present, is COxe2x80x94NH or COxe2x80x94NHxe2x80x94CH2xe2x80x94COxe2x80x94NH, and the sum p+q is 1 or 2;
(vii) chelate of the compound of formula I in which R2 and R4 are CONQ1Q2 and Q1 and Q2 are polyhydroxylated C2 to C6 alkyl groups optionally interrupted by an oxygen atom;
(viii) chelate of the compound of formula I in which Z is CH2 or CH2xe2x80x94COxe2x80x94NH, Zxe2x80x2 and Zxe2x80x3 are selected from COxe2x80x94NH and COxe2x80x94NHxe2x80x94CH2xe2x80x94COxe2x80x94NH, p and q are equal to 1, and R2 and R4 are CONQ1Q2. Preference is given, among these compounds, to those for which:
xe2x86x92R2 and R4 together comprise from 6 to 20 OH groups, or
xe2x86x92R1, R3 and R5 are identical and are selected from Br and I, and R2 and R4 each comprise from 6 to 10 OH groups.
(ix) Chelate of the compound of formula I in which the sum p+q is 0, R2 and R4 are the formula III and R1, R3 and R5 are identical and are selected from Br and I.
The invention also relates to a process for the preparation of the compounds of formula I which consists
in reacting the condensed macrocycle of formula 
xe2x80x83with a compound of formula Rxe2x80x2OOCxe2x80x94CHXxe2x80x94(CH2)2xe2x80x94COORxe2x80x2, in which X is a leaving group, such as a halogen atom, preferably bromine, or a (C1-C3) alkanesulphonate, tosylate or triflate group, and Rxe2x80x2 is H or (C1-C3) alkyl or benzyl, and in hydrolysing or hydrogenating the ester functional groups when Rxe2x80x2 is other than H, in order to obtain the hexaacid of formula 
in then reacting a salt or an oxide of the metal to be complexed with the hexaacid, in order to obtain the corresponding chelate or one of its salts with a base,
and, finally, in reacting the amine RNH2, in which R has the same meaning as in the formula I, with the chelate in the presence of an agent for activating the carboxylic acid functional groups, in order to obtain the triamide of formula I.
The acid of formula V and its metal chelates, in particular that of gadolinium, and their salts with a base, such as NaOH, which are intermediates in the synthesis of the products of formula I, are another subject-matter of the invention.
The invention also relates to compositions comprising a compound of formula I for magnetic resonance imaging, when M represents a paramagnetic cation, or for nuclear medicine, when M represents a radioelement, or for radiology, when M is the cation of a heavy atom which absorbs X-rays, it being possible for the said compositions to comprise the additives and vehicles usual for oral or parenteral administration.
Finally, the invention relates to medical imaging methods which consist in administering a composition comprising a compound of formula I to the patient and in observing the region to be studied obtained by magnetic resonance, by scintigraphy or using X-rays.
The diagnostic compositions of the invention can comprise, with a compound of formula I, additives such as antioxidants, buffers, osmolality regulators, stabilizers, calcium, magnesium or zinc salts, or low proportions of other chelates of these cations or of complexing compounds. Formulation examples appear in the general literature and in particular in Remington""s for Pharmaceutical Science, 18th Edition (1990), Mack. Pub. Co.
The unit doses will depend on the nature of the contrast agent, on the administration route, on the patient and in particular on the nature of the disorder to be studied. For intravenous injection and observation by magnetic resonance, the concentration of the solution will be between 0.001 and 0.5 mol/liter and, depending on the circumstances, from 0.001 to 0.1 millimol/kilo will be administered to the patient.
The contrast agents of the invention can be used to visualize the brain, organs such as the heart, liver or kidneys and all or part of the vascular system and to study the perfusion of these regions and to characterize permeability, tumoral, inflammatory or ischaemic anomalies.
The various stages of the synthesis of the compounds of the invention are carried out under conditions analogous to those described in the literature for reactions of the same type.
The macrocycle of formula IV can be prepared by the method of Richman and Atkins described in Inorg. Chem., 32, 5257-5265 (1993).
The nitrogen atoms are substituted, for example, by the action of an xcex1-bromoglutaric ester in the presence of an inorganic or organic base, such as NaOH, Na2CO3 or N(C2H5)3, in solution in a polar solvent, such as an alcohol, or, preferably, an aprotic solvent, such as acetonitrile or tetrahydrofuran.
The ester functional groups are hydrolysed by the action of a base or of an acid in aqueous or aqueous/alcoholic medium.
The complexing is carried out conventionally, for example as disclosed in U.S. Pat. No. 5,554,748 or in Helv. Chim. Acta, 69, 2067-2074 (1986).
To obtain the gadolinium chelate, GdCl3 or Gd2O3 can be reacted with the compound of formula V in aqueous solution at a pH of between 5 and 6.5. The cation of a complex derived from a compound of formula V or I can also be exchanged, when the relative stability of the two complexes permits it, in particular with an ion-exchange resin.
The relative percentage of the isomers in the mixture obtained, due to the presence of the three asymmetric carbons, can be modified by maintaining an aqueous solution of the chelate with a pH in the region of 3 at a temperature of greater than 80xc2x0 C. for a few days.
The amidation reaction can be carried out in aqueous medium, optionally in the presence of a third solvent, such as dioxane or tetrahydrofuran, with an activating agent, such as a soluble carbodiimide, for example those carrying an amine group described in J. Org. Chem., 21, 439-441 (1956) and 26, 2525-2528 (1961) or disclosed in U.S. Pat. No. 3,135,748 or carrying a quaternary ammonium group described in Org. Synth. V, 555-558, which relates to 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDCI) and 1-cyclohexyl-3-(2-morpholinoethyl) carbodiimide metho-p-toluenesulphonate. It can also be carried out with N-hydroxysulphosuccinimide, as described in Bioconjugate Chem., 5, 565-576 (1994), or 2-succinimido-1,1,3,3-tetramethyluronium tetrafluoro-borate and analogues, described in Tetrahedron Letters, 30, 1927-1930 (1989).
Another process consists in forming an intermediate activated ester by reacting, for example, N-hydroxysulphosuccinimide (NHS) or hydroxybenzotriazole (HOBT) in the presence of carbodiimide, such as EDCI, with the chelate V, which can be dissolved by salification with an inorganic cation, for example an ammonium or sodium.
With 2-ethoxy-l-ethoxycarbonyl-1,2-dihydro-quinoline (EEDQ), the reaction can be carried out in aqueous/alcoholic medium.
Some of the RNH2 amines are known compounds; the others will be prepared by analogous processes, preferably by attaching the phenyl nuclei step by step from the phenyl comprising the R1 to R5 groups and a substituent which is suitable for forming, depending on the circumstances, Z, Zxe2x80x2 or Zxe2x80x3.
Reference may also be made to Patents WO 96/09281 or WO 97/01359 for the preparation of those in which Z is CH2CONH, p=q=0, R1=R3=R5=halogen or H, and R2=R4=CONQ1Q2.
In some of the precursor aminoalcohols HNQ1Q2, Q1 and/or Q2 represent the CH2(CHOH)n(CH2OCH2)r(CHOH)tCH2OH group with t=0, r=0 or 1 and n=0 to 4; they can be prepared
from a primary alkylamine or aminoalcohol, with which a sugar is reacted, before carrying out the reduction of the imine obtained, as disclosed in EP-A-675105 or EP-A-558395,
or from benzylamine, with which a sugar and then an optionally hydroxylated C1-C6 alkyl sulphate or halide are reacted, before removing the benzyl group by catalytic hydrogenation.
Different stereoisomers will be obtained, depending on the configuration of the sugar reacted.
The aminoalcohols can, when r=1 and n=t=0, be prepared from 2-aminoethoxyethanol, with which is reacted a suitably hydroxylated alkyl halide or epoxide or alternatively a hydroxylated aliphatic aldehyde, such as a monosaccharide, in order to form an imine, subsequently reduced catalytically or chemically.
When r=n=1, the aminoalcohols can be prepared by reaction of the epoxide 
with the appropriate primary aminoalcohol, the said epoxides being obtained by oxidation of the corresponding ethylenated derivatives by a peracid or a peroxyimidic acid, as described in J. Org. Chem., 26, 659-663 (1961) and 48, 888-890 (1983).
Mention may be made, among the aminoalcohols prepared by these methods, of those for which Q1=CH2(CHOH)4CH2OH and Q2=Q1 or CH2 (CHOH) CH2OH Q1=CH2(CHOH)2CH2OH and Q2=CH2CHOHCH2O(CH2)2OH or (CH2)2OCH2CHOHCH2OH Q1=CH2(CHOH)3CH2OH and Q2=(CH2)2O(CH2)2OH.
In the case where p and/or q are other than zero, the Zxe2x80x3 bridge will be formed between the two phenyl nuclei, depending on the circumstances, before or after the Zxe2x80x2 bridge.
For example, the compound 
can be prepared, when Z is a bond, from the diphenyl derivatives VII or their esters. 
in which Zxe2x80x2 has the same meaning as in the formula II.
The compound VII in which Zxe2x80x2 is O is described in Makromoleculare Chemie, 130, 103-144 (1969), that in which Zxe2x80x2 is NH is described in Indian J. Chem., 13, 35-37 (1975), that in which Zxe2x80x2 is CH2 or CO is described in J. Pharm. Sci., 55(3), 295-302 (1966), that in which Zxe2x80x2 is a bond is described in Synth. Comm., 24(22), 3307-3313 (1994) and that in which Zxe2x80x2 is S is described in Il Farmaco, 44(7-8), 683-684 (1989).
Other compounds vII can be prepared by analogous processes; for example, when Zxe2x80x2 is HNCONH, by reaction of O2NC6H4NCO with H2NC6H4COOH in anhydrous medium or, when Zxe2x80x2 is NHCO or CONH, by reaction of the aromatic acid chloride with the appropriate aniline in solution in an aprotic solvent, such as CH2Cl2, C6H5CH3 or CH3CON(CH3)2, or by reaction of the aromatic acid with the aniline in the presence of sulphonic acid chloride, of triethylamine and of dimethylaminopyridine, as described in Synth. Communications, 25(18), 2877-2881 (1995).
The reduction of the NO2 group of VII to NH2 can be carried out in a known way with hydrogen in the presence of catalysts or chemically.
When Z in the formula VI is CH2xe2x80x94CONH, glycine, the acidic functional group of which is activated and the NH2 group of which is protected, is reacted with a compound VI in which Z is a bond or with aniline carrying a precursor group for Zxe2x80x2, which is optionally protected.
The glycine is protected, for example, in the carbamate form, in particular t-butyl carbamate (Synthesis, 48,(1986)) and benzyl carbamate (Chem. Ber., 65, 1192 (1932)), in the phthalimide form (Tetrahedron Letters, 25, 20, 2093-2096 (1984)), with a benzyl (Bull. Soc. Chim. Fr., 1012-1015 (1954)) or with an N-allyl (Tetrahedron Letters, 22, 16, 1483-1486 (1981)). (See also Protective Groups in Organic Synthesis, 315-349, T. W. Greene (John Wiley and Sons Inc.)). The protective group for the NH2 attached to Z is generally removed only after the R group has been constructed; conventionally, a phthalimido group is removed by the action of hydrazine, whereas a benzyloxycarbonyl or benzyl group is removed by catalytic hydrogenation.
When Z=CH2 and Zxe2x80x2=CONH or CONHCH2CONH, 4-aminomethylbenzoic acid, in which the NH2 group is protected in the carbamate or imide form as described in J. Org. Chem., 43, 2320-2325 (1978) or in Rec. Trav. Chim. Pays-Bas, 79, 688 (1960), can be reacted with the substituted benzoic acid, the acidic functional group of which is blocked by esterification.
When Z is (CH2)2NHCO, RNH2 can be prepared by reaction of an excess of ethylenediamine with an appropriate benzoic ester carrying a precursor group for Zxe2x80x2, which is optionally protected, or a more complete fraction of R.
The compound VI, after protection of the NH2 group and activated in the acid chloride form or by a peptide coupling agent, will react with the precursor group for Zxe2x80x3 carried by the terminal phenyl nucleus, suitably substituted by R1 to R5, to give RNH2 after deprotection.
The conditions for the preparation of the RNH2 amines will be better understood on reading the examples which follow. The mass spectra (electrospray) of these products, such as those of the examples, correspond to the expected structures.
Compounds A and Axe2x80x2
RNH2 with 
Compound A
35 g of D-galactose are dissolved in 100 ml of methanol comprising 17 g of 3-aminopropanediol and the mixture is kept stirred at 25xc2x0 C. for 12 hours, before introducing 5 g of 10% palladium-on-charcoal catalyst and 40 ml of water in order to hydrogenate the imine at 60xc2x0 C. The catalyst is removed by filtration and the mixture is concentrated to 85 ml. The aminoalcohol is isolated by precipitation when the concentrated solution is introduced into 30 ml of isopropanol at approximately 35xc2x0 C.
156 g of bromine are slowly introduced into 300 ml of an aqueous solution of 50 g of 5-aminoisophthalic acid and 55 ml of 37% hydrochloric acid. After stirring overnight, the excess bromine is neutralized by addition of an aqueous sodium bisulphite solution, before isolating the precipitate. Yield: 90%.
27 ml of thionyl chloride are slowly introduced into a solution of 69 g of N-phthaloylglycine in 200 ml of dimethylacetamide at 10xc2x0 C. and then, after stirring for 2 hours, 100 g of the acid obtained above are introduced at approximately 15-20xc2x0 C. After leaving overnight at room temperature, the mixture is poured into 800 ml of warm water. 140 g of final product are thus isolated.
70 ml of thionyl chloride are slowly introduced at 18xc2x0 C. into a solution of 100 g of the diacid in 300 ml of dioxane and 50 ml of dimethylformamide. The yellow precipitate formed after stirring for 3 days at room temperature is filtered off and washed with methyl t-butyl ether. 70 g of beige solid are thus obtained.
125 g of the galactitol-derived amine obtained in (a) are dissolved in 610 ml of N-methylpyrrolidone at 80xc2x0 C. before introducing, at 60xc2x0 C., 17 g of Na2CO3 and 102 g of the diacid chloride. After two hours at this temperature, the reaction mixture is brought back to room temperature and then filtered. The filtrate is introduced into 1.5 liters of isopropanol; the precipitate formed is dissolved in water and chromatographed on an ion-exchange resin in the H+ form in order to remove the starting amine. 136 g of solid product are thus isolated.
125 g of the preceding phthalimide are dissolved in 520 ml of N-methylpyrrolidone and 175 ml of water at 70xc2x0 C and 8 ml of hydrazine hydrate are added before maintaining the mixture for two hours at 90xc2x0 C. This mixture is subsequently cooled to approximately 20xc2x0 C. and then poured into 1.6 liters of ethanol. The precipitate formed is purified by passing its aqueous solution through an ion-exchange resin in the H+ form.
Compound Axe2x80x2
(axe2x80x2) By reacting 3-aminopropanediol with D-glucose under the same conditions as described hereinabove in stage (a) for the preparation of the compound A, 1-deoxy-1-(2,3-dihydroxypropyl)amino-D-glucitol is obtained.
The compound Axe2x80x2 can be obtained by carrying out stages (b) to (f) described hereinabove for the preparation of the compound A from the glucitol-derived amine obtained in (axe2x80x2) or else by carrying out the following stage (exe2x80x2).
(exe2x80x2) 95 g of the glucitol-derived amine obtained in (axe2x80x2) are dissolved in 460 ml of dimethylacetamide at 90xc2x0 C. before introducing, at 65xc2x0 C., 32 ml of triethylamine and 117 g of the diacid chloride described in the above stage (d) in the preparation of the compound A. After 4 h 30 at 55-60xc2x0 C., the reaction mixture is brought back to room temperature and filtered. The solution obtained, at 50xc2x0 C., is slowly poured into an aqueous hydrazine solution (11 ml in 115 ml of water) ; after 3 hours at 80xc2x0 C., the mixture, brought back to room temperature, is acidified to pH 1 by addition of an N aqueous HCl solution. The precipitate is separated off and the filtrate is poured into 3 liters of ethanol with stirring. The precipitate formed is dried and then purified by diafiltration, in order to remove most of the molecules of low mass, and the solution obtained is chromatographed on anion- and cation-exchange resins. Yield 60%.
The final amine can be freeze-dried.
HPLC analysis on Column 2 with Eluent 2: CF3COOH in water pH 3.3/CH3CN
Compound B
RNH2 with 
A mixture of 10 g of 4-aminomethylbenzoic acid, 14.5 g of carbethoxyphthalimide, 9.2 ml of triethylamine and 140 ml of tetrahydrofuran is maintained for 72 hours at reflux temperature. The precipitate formed is isolated at room temperature; after washing with an aqueous acidic solution and drying, 14.5 g of product are obtained. M.p.=264xc2x0 C.
1 g of tricaprylylmethylammonium chloride (Aliquat(copyright) 336) and 5.3 ml of thionyl chloride are introduced into a solution of 13.5 g of the acid in 55 ml of dioxane. After stirring for 12 hours at 80xc2x0 C., the mixture is concentrated to dryness and the residual solid is washed with diisopropyl ether. w=14 g.
14 g of the acid chloride and 15 g of 5-amino-2,4,6-tribromoisophthalic acid are dissolved in 50 ml of N-methylpyrrolidone and the mixture is maintained at 100xc2x0 C. for several hours. The solution, at approximately 20xc2x0 C., is poured into 300 ml of water and the precipitate formed is recrystallized from isopropanol to give 5.5 g of final product.
HPLC (high performance liquid chromatography): Column No. 1: Symmetry(copyright) C18; 100 xc3x85; 5 xcexcm; l=25 cm; d=4.6 mm (Waters).
Eluent No. 1: CH3COONH4 in water (0.005 M)/CH3CN.
Gradient: 80% to 20% (v/v) over 15 minutes; Flow rate 1 ml/minute;
tr=4.5 minutes.
5.6 ml of dimethylformamide and 9 ml of thionyl chloride are introduced into a solution of 5.5 g of the acid in 40 ml of dioxane while maintaining the temperature at less than 5xc2x0 C. After 30 minutes, the mixture is poured into 150 ml of water and the precipitate formed is isolated. w=4.6 g.
2.3 g of the acid chloride are introduced into a solution of 4 g of the aminoalcohol 1-deoxy-1-(2,3-dihydroxypropyl)amino-D-galactitol in 15 ml of N-methylpyrrolidone at 65xc2x0 C. After 3 hours 30, 4 ml of water are added and the mixture is brought to 90xc2x0 C. before adding 0.3 ml of hydrazine hydrate. After 2 hours at 90xc2x0 C., the solution is poured, at room temperature, into 80 ml of ethanol. The isolated precipitate is dissolved in 10 ml of water and the solution, at pH 1, is purified by chromatography through an anionic resin in the OHxe2x88x92 form, of the Amberlite(copyright) type, then through a cationic resin in the H+ form, of IMAC(copyright) type, and finally through an OHxe2x88x92 anionic resin. 2 g of amine are obtained.
HPLC: Column No. 2: LiChrospher(copyright); 100 RP18; 5 xcexcm; 1=25 cm; d=4 mm (Merck(copyright)).
Eluent No. 2: CF3COOH in water pH 3.3/CH3CN.
Gradient: 98% to 77% (v/v) over 25 minutes; Flow rate 1 ml/minute;
tr: 18 to 22 minutes.
Compound C
RNH2 with 
2.3 g of the acid chloride prepared according to the preceding stage (d) are introduced into a solution at 65xc2x0 C. of 5.5 g of disorbitylamine in 30 ml of N-methylpyrrolidone. After 4 hours at 65xc2x0 C., 8 ml of water are introduced and then, at 90xc2x0 C., 0.3 ml of hydrazine hydrate; after 2 hours at this temperature, the reaction mixture, at approximately 20xc2x0 C., is poured onto 130 ml of water. The precipitate formed is washed with ethanol and then redissolved in 10 ml of water, and the solution is brought to a pH of 1.5 and then purified by chromatography through anionic and cationic resins. 1.7 g of the amine are thus obtained.
HPLC: Column No. 2; Eluent No. 2;
tr: 18 minutes.
Compound D
RNH2 with 
1. 15 g of disorbitylamine are dissolved in 60 ml of N-methylpyrrolidone at 80xc2x0 C. and 1.6 g of dry sodium carbonate are introduced into the mixture at 60xc2x0 C., followed by 9.6 g of 5-(phthalimidoacetamido)-2,4,6-tribromoisophthalic acid chloride. After stirring for 1 hour at this temperature and 16 hours at room temperature, the precipitate is removed and the solution is poured into 160 ml of isopropanol. The isolated precipitate weighs 20 g.
2. Hydrazinolysis:
20 g of the preceding product and 1.7 ml of hydrazine hydrate are introduced into 40 ml of water at 70xc2x0 C. After stirring for 3 hours, the mixture is acidified to pH 4 by addition of 6N hydrochloric acid at room temperature. The precipitate formed is then removed and the filtrate neutralized by addition of a 1N aqueous NaOH solution. The excess hydrazine is removed by reverse osmosis. The residual solution is treated with 1 ml of strong cationic resin and then 6.5 ml of weak anionic resin.
The final product is then extracted from the solution by attaching to a strong cationic resin in the H+ form, from where it is eluted with a dilute aqueous NaCl solution (0.1M). w=8 g.
HPLC: Column No. 2; Eluent No. 3;
Gradient: CF3COOH in water (pH 3.4)/CH3CN from 95% to 50% (v/v) over 50 minutes; flow rate 1 ml/minute;
tr: 7 minutes.
10 g of 4-nitrobenzoic acid chloride are slowly introduced into 7.4 g of 4-aminobenzoic acid and 36 ml of dimethylacetamide while maintaining the temperature at less than 25xc2x0 C. After stirring for 24 hours, 50 ml of methylene chloride are added at 10xc2x0 C. in order to precipitate the desired product. After washing with water and drying, 14.5 g of product are isolated.
A suspension of 13.6 g of the preceding acid in 180 ml of water, to which has been added 24 ml of 1N aqueous NaOH solution and 1.4 g of palladium-on-charcoal (10%), is subjected to a hydrogen pressure of 0.6 MPa for 4 hours.
The pH of the final suspension is then brought to approximately 10 before filtration through Celite(copyright) in order to remove the catalyst. The precipitate formed during the acidification of the filtrate to pH 5.3 is isolated and dried.
w=10.6 g; M.p.  greater than 260xc2x0 C.
3.2 ml of thionyl chloride are introduced dropwise into a solution of 9 g of phthalimidoacetic acid in 40 ml of dimethylacetamide at 10xc2x0 C. and then, after stirring for 3 hours, 10.5 g of the amino acid obtained previously are introduced at a temperature of less than 20xc2x0 C.
After stirring for 12 hours, the mixture is poured into 400 ml of water and the isolated precipitate is washed with warm water. Weight after drying: 18 g. M.p.  greater than 260xc2x0 C.
2.5 ml of thionyl chloride are introduced into 10 g of the acid suspended in 50 ml of dioxane and 1 ml of dimethylformamide, and the mixture is kept stirred at 50xc2x0 C. for 5 hours. After addition of one volume of diisopropyl ether, 10 g of precipitate are isolated.
The acid can also be suspended in toluene with tricaprylylmethylammonium chloride as catalyst.
A solution of 2.25 g of the acid chloride with 5 g of N,Nxe2x80x2-bis(2,3,4,5,6-pentahydroxyhexyl)-2,4,6-tribromo-5-(glycylamino)isophthalamide and 0.7 ml of triethylamine in 25 ml of dimethylacetamide or of N-methylpyrrolidone is kept stirred for 12 hours and then poured into 60 ml of ethanol. 6.2 g of precipitate are thus isolated.
HPLC: Column No. 2; Eluent No. 3;
tr=27-35 minutes (mixture of isomers).
A solution of 0.6 ml of hydrazine hydrate in 10 ml of water is introduced into a solution of 10 g of the preceding phthalimide in 40 ml of dimethylacetamide at 80xc2x0 C. After stirring for 3 hours at this temperature, the cooled mixture is poured into 125 ml of ethanol. 9 g of precipitate are isolated, which product is purified by treatment of its aqueous solution with a strong anionic (OHxe2x88x92) resin and then a weak cationic (H+) resin.
w=8 g.
The reaction mixture can also be acidified in order to separate the precipitated phthalohydrazide and to remove the solvent and the molecules of low mass by ultrafiltration, before final precipitation from aqueous ethanol.
HPLC: Column No. 2; Eluent No. 3 but 90/10 (v/v) in isochratic elution at 1 ml/minute;
tr=28-35 minutes.
Compound E
RNH2 with 
50 9 of para-nitrobenzoic acid chloride and 75 g of 5-amino-2,4,6-tribromoisophthalic acid in 400 ml of dioxane are maintained for 18 hours at the reflux temperature. After cooling, the precipitate is filtered off, washed with 50 ml of dioxane and dried.
w=115 g.
A solution of 180 g of the preceding nitro derivative in 600 ml of water is brought to pH 6 by addition of a 5N aqueous NaOH solution and hydrogenated under a pressure of 5xc3x97105 Pa in the presence of type 156 Pt (Johnson Matthey) for 7 hours. The catalyst is separated off by filtration and the water is evaporated under reduced pressure. w=80 g.
HPLC: Column No. 2; Eluent No. 4; CF3COOH in water (pH 2.8) with methanol (99/1, v/v); flow rate 1 ml/minute;
tr: 3.6 minutes (18.8 minutes for the nitro derivative).
A mixture of 10 g of 4-aminomethylbenzoic acid, 14.5 g of N-carbethoxyphthalimide and 9.2 ml of triethylamine in 140 ml of tetrahydrofuran is maintained at its reflux temperature for 72 hours. The precipitate, isolated by filtration at room temperature from the reaction mixture, is washed with diethyl ether and a 1N aqueous hydrochloric acid solution. 14.5 g of solid are obtained, 12.2 g of which are dissolved at 10xc2x0 C. in 90 ml of N,N-dimethylacetamide and 3.5 ml of thionyl chloride; after stirring for 3 hours, 23.4 g of the aniline obtained in the preceding stage are introduced into the mixture and the mixture is left stirring overnight, before being poured into 900 ml of water. The isolated precipitate, washed with water, is recrystallized from 200 ml of dioxane.
w=30 g.
HPLC: Column No. 2; Eluent: CF3COOH in H2O (0.1M)/CH3CN (90/10, v/v) with a gradient after 20 minutes up to 40/60 over 30 minutes; flow rate 1 ml/minute;
tr=26 to 29 minutes.
30.3 g of the isophthalic derivative obtained in the preceding stage are dissolved in 150 ml of dioxane comprising 26 ml of dimethylformamide and 42 ml of thionyl chloride are introduced dropwise at 5xc2x0 C. After 30 minutes at 0xc2x0 C., the mixture is poured into 550 ml of water and the precipitate formed is filtered off and washed with water and with diisopropyl ether. w=26 g after drying.
1. 10 g of the acid dichloride are introduced into a solution of 15 g of 1-deoxy-l-(2,3-dihydroxypropyl)amino-D-galactitol in 100 ml of N-methylpyrrolidone at 60xc2x0 C. After stirring for 4 hours at this temperature, the mixture, brought back to room temperature, is poured into 1 liter of isopropanol. The precipitate formed is isolated and dried.
HPLC: Column No. 2; Eluent No. 5: CH3COONH4 in H2O (0.01M) /CH3CN; 85% to 50% (v/v) gradient over 20 minutes; flow rate 1 ml/minute;
tr=16 minutes. 2. Removal of the phthalimide group:
20.4 g of the preceding solid are introduced with stirring into 80 ml of N,N-dimethylacetamide at 80xc2x0 C., followed by 1.6 ml of hydrazine hydrate in solution in 20 ml of water. After 3 hours at this temperature, the reaction mixture is poured at room temperature into 1 liter of ethanol. The precipitate formed is isolated, dried and then dissolved in 40 ml of water. Approximately 2 ml of 6N aqueous HCl solution are introduced at 0xc2x0 C. in order to lower the pH to 2; the mixture is filtered through Celite(copyright) and then purified by passing through ion-exchange resins (anionic Amberlite(copyright) and cationic IMAC(copyright)). 6 g of the desired product are then obtained.
HPLC: Column No. 2; Eluent No. 5
tr=24 to 29 minutes.
Compound F
RNH2 with: 
(a) 50 g of 1-deoxy-1-(2,3-dihydroxypropyl)amino-D-galactitol are dissolved in 300 ml of dimethylacetamide at 120xc2x0 C. and then 38 g of 5-(phthalimidoacetamido)-2,4,6-triiodoisophthalic acid chloride (prepared according to U.S. Pat. No. 4,283,381) and 17 ml of triethylamine are rapidly added at 80xc2x0 C. After stirring for 5 hours at 80xc2x0 C., the mixture is filtered at room temperature, the filtrate is introduced into 800 ml of isopropyl alcohol and the precipitate is isolated and dried.
The excess starting aminoalcohol is removed by chromatographing the aqueous solution of this prepitate through H+ resin.
The phthalimide group is hydrazinolysed in aqueous medium to produce N,Nxe2x80x2-bis(2,3,4,5,6-pentahydroxyhexyl)-N,Nxe2x80x2-bis(2,3-dihydroxypropyl)-2,4,6-triiodo-5-(glycylamino)isophthalimide.
(b) 23 g of 5-(phthalimidoacetamido)-2,4,6-triiodoisophthalic acid chloride and 12 ml of triethylamine are added to 70 g of the amine obtained in (a) in solution in 200 ml of dimethylacetamide. After stirring for 24 hours at room temperature, the reaction mixture is poured into 1500 ml of isopropyl alcohol and the precipitate formed is isolated.
The crude phthalimide thus obtained, in solution in 160 ml of water at pH 5, is chromatographed through 650 g of Amberlite(copyright) XAD 16 resin, elution being carried out with a water/methanol (65/35 v/v) mixture. The amino group of the phthalimide is deprotected by hydrazinolysis: 57 g of phthalimide are treated with 3 ml of NH2xe2x80x94NH2 in 200 ml of water at 80xc2x0 C.; after 3 hours, the phthalohydrazide is precipitated at pH 1 and the filtrate is evaporated to give an oil, which is purified by precipitation from ethanol and chromatographed through anionic-exchange resin (weakly basic Amberlite(copyright)) and cationic-exchange resin (IMAC HPIII from Rxc3x6hm and Haas).
Analytical HPLC: Column No. 2; Eluent No. 8: H2O/CH3CN; 95% to 80% gradient over 45 minutes.
tr: 33 to 49 minutes.
Under the same conditions, the amine obtained in (a) is defined by tr=6 to 16 minutes.
Another mixture of isomers of the compound F can be prepared by applying the above procedure to 1-deoxy-1-(2,3-dihydroxypropyl)amino-D-glucitol.
Analytical HPLC: Column No. 2; Eluent No. 8
Product obtained in the corresponding stage (a): tr=7 to 24 minutes
Final product: tr=30 to 40 minutes.
In that which follows, the preparation of certain chelates of the invention is described by way of illustration.